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Scientific result | MRI | Brain

A sensory response imaged on a microscopic and mesoscopic scale.

​Researchers from Inserm, in collaboration with a team from NeuroSpin, have developed a preparation to observe sequentially the neuronal activity and vascular responses of the same mouse with bi-photonic microscopy, ultrasound imaging and BOLD-fMRI, in response to an olfactory stimulus. This approach made it possible to quantitatively compare the responses to odors observed both at the microscopic and mesoscopic scales. Results, published in Nat. Comm, show that the three techniques similarly measure the concentration of an odor.

Published on 25 March 2019

​Abstract of the original paper

Imaging based on blood flow dynamics is widely used to study sensory processing. Here we investigated the extent to which local neuronal and capillary responses (two-photon microscopy) are correlated to mesoscopic responses detected with fast ultrasound (fUS) and BOLD-fMRI. Using a specialized chronic olfactory bulb preparation, we report that sequential imaging of the same mouse allows quantitative comparison of odour responses, imaged at both microscopic and mesoscopic scales.
Under these conditions, functional hyperaemia occurred at the threshold of neuronal activation and fUS-CBV signals could be detected at the level of single voxels with activation maps varying according to blood velocity.
Both neuronal and vascular responses increase non-linearly as a function of odour concentration, whereas both microscopic and mesoscopic vascular responses are linearly correlated to local neuronal calcium.

These data establish strengths and limits of mesoscopic imaging techniques to report neural activity.

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